Progressive-burning smokeless powder



Patented Nov. 7, 1939 UNHTEEE @TATES .ZJWBEZ E ATENT EQ lPRiIlGRlESSIVE-BEJRNHNG SMOKELESS POWDER No Drawing. Application October 6, 1938, Serial No. 233,595

'7 Claims.

This invention relates to smokeless powder, and particularly to coated, deterred, or progressiveburning smokeless powder.

Smokeless powder, on combustion in the chamber of the gun in which it is used, tends to burn initially at a more rapid rate than is desired and thus produces high breech pressures. This defect is not overcome by using larger grains of powder,

in the case of those powders intended to give maximum results in center-fire rifle cartridges.

Many attempts have been made in the past to deter the initial rate of burning of the powder grains by coating said grains with an agent, explosive or non-explosive, which will slow down the initial rate of combustion of the powder grains, thus extending the period of time taken by the grains to burn completely, and in this way reduce the otherwise high breech pressure in the gun. The coating material used, penetrates the powder grains more or less, so that, as the powder grains burn, the successively exposed surfaces contain, gradually, less and less of the deterrent material, thus causing subsequent combustion of the powder grain to proceed with increasing speed as the bullet travels down the bore of the gun.

In the past,,many substances have been used, without complete success, to coat smokeless powder grains, e. g., such materials as diethyldiphenylurea, dimethyldiphenylurea, dinitrotoluene, al-

kyl phthalates, or mixtures thereof, and various methods of applying such deterrent substances have been known.

The known methods of deterring or coating smokeless powders have not been completely effective in that they have not produced smokeless powders of high gravimetric density combined with high ballistic stability. By ballistic stability is meant the maintenance, with age, of the initial ballistics produced by the powder. For example, many of the coating agents continue to penetrate into the powder grain, particularly in warm climates, and thus alter their deterrent characteristics.

With modern loads of deterred smokeless powder it is usual to find that the maximum velocity which can be obtained with a given projectile is limited, not by the maximum allowable pressure produced in the chamber of the gun, but by the powder capacity of the cartridge. However, an increase in the gravimetric density of the powder would permit the use of greater powder charges and result in an increased velocity of projectile.

It is the object of this invention to produce a coated smokeless powder which is ballistically stable with age and ofhigh gravimetric (or loading) density. The high gravimetric density of my coated powders enables me to use greater charges than hitherto permitted by the volumetric capacity of the cartridge", which is a distinct improvement over prior art powders and an advantage which has been sought for many years by the art. In addition, my improved smokeless powder is not subject to clustering or sticking together of the grains.

In the preparation of coated smokeless powder in accordance with my invention, I use as coating agentsthe lower alkyl esters of benzoyl-bem zoic acid which are characterized by having a melting point within the range from about 35 C. to about 110 C. Among these esters which I-have found suitable vas coating agents for smokeless powder are ethyl ortho benzoyl benzoate and methyl ortho benzoyl benzoate. Smokeless powder may be coated with these compounds alone or with mixtures thereof or in combination with other coating agents.

I may use as the powder grain to be coated either a single base (nitrocellulose) powder, or a double base (nitrocellulose-nitroglycerin) powder. Although the powder grain may be of any size, I have found that my coating agents ofier the most advantage when used with the larger caliber powders.

In practicing my invention the herein specified coating agents are applied to the smokeless powder as a solution of said coating agents in a volatile solvent which is substantially a non-solvent for the smokeless powder. Among the volatile solvents which I have used are toluene, ethylene dichloride, petroleum naphtha, isopropyl alcohol and ethyl alcohol and of these, I prefer using 95% by Volume ethyl alcohol. To 100 parts by weight of smokeless powder I add from about 1 to about 10 parts by weight of the spebified coating agents, dissolved in a suitable quantity of solvent. The 40 smokeless powder is treated with the coating agent in any suitable manner, for example, by tumbling the powder and the coating agent solution in a barrel at a temperature within the range from about 10 C. to about 95 C. for a period of time between about 5 minutes to about 4 hours, after which the powder, so coated, may be subjected to. further heat treatment to eliminate any remaining solvent,,if this appears desirable. The time and temperature of treatment, as well as the quantity of coating agent will, necessarily, be varied with the size of the powder grain employed, the type of firearm in which the powder is to be used, etc. In the case of application of extremely heavycoatings to the powder, water maybe added to the coated powder grains before elimination of all of the volatile solvent, in order to prevent sticking and clustering of the grains.

As specific illustrations of the carrying out of my invention, the following examples are given:

Example 1 Nine hundred and seven parts by weight of a double base, smokeless powder, containing 20% nitroglycerin, pressed through a 0.045 inch die having a 0.015 inch pin, and the strand so proproduced cut into 11 particles per inch was placed in a sweetie barrel maintained at C., and to this was added 45.3 parts by weight of ethyl ortho benzoyl benzoate dissolved in 160 parts by weight of ethyl alcohol, the mixture tumbled in the closed sweetie barrel for about /2 hour at 75 C., then for another hour at C., after which time the powder was removed to a dry house and dried for 3 days at 55 C., then graphited, screened, and exposed to an atmosphere of 50-60% relative humidity to bring the moisture content to equilibrium. A yield of of unclustered power was obtained having a gravimetric density of 0.942.

Example 2 Nine hundred and seven parts by weight of the same powder as in Example 1 was surface coated, in the same manner as in Example 1, with 45.3 parts by weight of methyl ortho benzoyl benzoate, then finished in the same manner. A yield of 96% of unclustered powder was obtained having a gravimetric density of 0.937.

Example 3 cartridge case using a grain bullet, the cartridge being loaded in each case with sufiicient powder to fill said cartridge to the base of the bullet. The results obtained are shown in the following table: 9

Charge Mean velocity Powder fromin over 153 foot- Mean pressure grains range Ft./ser. Lbalsq. inch Example 1 62. 1 208 38, 300 Example 2 62. 5 3, 437 44, 500 Example 8 cl. 1 2, 880 26, 900

It will be noted in the above table that powders coated with the agents disclosed by the present invention have an appreciable velocity increase over comparator Example 3 in which a prior art coating material is used. Furthermore, in comparison with Example 3 it will be noted that a greater charge of powder can be utilized in the same space in the cartridge in the case of examples 1 and 2 which is of course due to the higher gravimetric densities of powders prepared in accordance with this invention.

To illustrate the improvement in stability obtained by my coated powders, I subjected some of these to warm storage using for comparison a powder coated in the same manner with butylphthalyl butylglycollate. These results are shown in the following table:

The improvement in ballistic stability is apparent from the above table.

The following additional examples are shown further illustrating the advantages of coatin powder with my new coating agents.

' Example 4 Nine hundred and seven parts by weight of the same smokeless powder as in Example 1 was placed in the sweetie barrel maintained at 60 C., (5 C. above the melting point of the coating material used), and 45.3 parts by weight of ethyl ortho benzoyl benzoate, dissolved in 160 parts by weight of ethyl alcohol added, the mixture tumbled in the closed sweetie barrel for 1 hour at 60 C., after which time the powder was dried, graphited, screened, and finished as in the preceding examples. A yield of 92.6% of unclustered powder was obtained having a gravimetric density of 0.950.

In comparsion therewith, 'I surface coated 907 parts by weight of the same smokeless powder with 45.3 parts by weight of Centralite #1, maintaining the temperature of the sweetie barrel at 75 C., i. e., 5 C. above the melting point of Centralite #1, for 1 hour, otherwise following the same pro cedure. A yield of 52.2% of unclustered powder was obtained having a gravimetric density of 0.925.

Example 5 Eighteen hundred and fourteen parts by weight of the same double base smokeless powder as in Example 1, was placed in the sweetie barrel maintained at 60 C. and to this was added 81.6 parts by weight of ethyl ortho benzoyl benzoate dissolved in 320 parts by weight of ethyl alcohol and the mixture then tumbled in the closed sweetie barrel for of an hour at 60 C. and with the barrel open for of an hour at the same temperature. After this treatment the powder was removed from the barrel and dried for 3 days at about 55 C. then graphited and exposed to an atmosphere of 50 to 60% relative humidity to bring the moisture content to equilibrium. The yield of unclustered powder was 99%.

Another sample of this powder was coated in an identical manner with 90.7 parts of the same compound. The yield of unclustered powder was the same as above.

One hundred and fifty parts by weight of the first coated powder was blended with 600 parts by weight of the second, the powder so obtained having a gravimetric density of 0.929. 55.5 grains of this powder filled a .30 caliber model 1906 cartridge case to the base of the 173 grain boat tail bullet. This powder charge gave the bullet an average veloci y of 2933 feet per second over a range of feet, and produced an average breech pressure of 54,000 pounds per square inch.

Example 6 Eighteen hundred and fourteen parts by weight of a double base smokeless powder with the same characteristics as in Example 1 was placed in the sweetie barrel maintained at 60 C. and to this was added 90.7 parts by weight of methyl ortho benzoyl benzoate dissolved in about 320 parts by Weight of ethyl alcohol. This mixture was then tumbled in the closed sweetie barrel for one hour at 60 0., after which the powder was removed and dried for three days at about 55 C. It was then graphited and exposed to an atmosphere of 50% to 60% relative humidity to bring the moisture content to equilibrium. The yield of unclustered powder was 99%.

Nine hundred and seven parts by weight of this same powder was coated in identical manner with 49.9 parts by weight of methyl ortho benzoyl benzoate, dissolved in 160 parts by weight of ethyl alcohol. The yield of unclustered powder in this case was 97%.

Seven hundred and twenty parts by weight of the first coated powder was blended with 80 parts by weight of the second coated powder, this combined powder having a gravimetric density of 0.934. 55:6 grains of this powder filled a .30 caliber model 1906 cartridge case to the base of a 173 grain boat tail bullet and this powder charge gave the bullet an average velocity of 2935 feet per second over a 150 ft. range and produced an average breech pressure of 54,400 pounds per square inch.

Example 7 Eighteen hundred and fourteen parts by weight of a double base smokeless powder prepared as before was placed in a sweetie barrel maintained at 60 C. and to this was added 72.5 parts by weight of symmetrical diethyldiphenylurea dissolved in 320 parts by weight of ethyl alcohol. This powder was then treated in the same manner as that in Example and produced a yield of unclustered powder of only 85%.

Another sample of this powder was coated in the identical manner with 81.6 parts of the same coating agent. In this case, the yield of unclustered smokeless powder was only 79%.

Two hundred parts by weight of the first coated powder was blended with 800 parts by Weight of the second coated powder, producing a mixture having a gravimetric density of 0.904. 55.0 grains of this powder filled a .30 caliber model 1906 cartridge case to the base of 173 grain boat tail bullet. This powder charge gave the bullet an average velocity of 2895 feet per second over a 150 foot range, and produced an average breech pressure of 53,900 pounds per square inch.

Example 8 Eighteen hundred and fourteen parts by weight of a singlebase powder was pressed through a 0.045 die having a 0.010 pin, the strand so produced being cut into 11 particles per inch. These particles were placed in a sweetie barrel maintained at 75 to 85 C. and to this was added 126.8 parts by weight of ethyl ortho benzoyl benzoate dissolved in 362 parts by weight of ethyl alcohol. The mixture was tumbled in the closed sweetie barrel for about 1 hour at 75 to 85 C. after which the powder was removed and dried for three days at about 55 C. and then graphited. The yield of unclustered powder was 99%, and the gravimetric density thereof 0.918.

The same amount of this powder was coated in an identical manner with 126.8 parts by weight of symmetrical diethyldiphenylurea. In this case the yield of unclustered powder was 95% and the powder had a gravimetric density of .899.

Example 9 Eighteen hundred and fourteen parts by weight of a double base smokeless powder containing 20% nitroglycerine was pressed through a 0.070 die having a 0.015 pin and the strand so produced cut into 11 particles per inch. These particles were placed in a sweetie barrel maintained at 75-85 C. to which was added 126.8 parts by weight of ethyl ortho benzoyl benzoate dissolved in 362 parts by weight of ethyl alcohol. The mixture was then tumbled in a closed sweetie barrel for about 1 hour at 75-85 C., after which the powder was removed and dried for 3 days at about 55 C. and then graphited. 77.9 per cent of this powder was free of clusters or double grains and had a gravimetric density of 0.885.

A similar amount of this powder was coated in an identical manner with the same amount of symmetrical diethyldiphenylurea. This powder had a gravimetric density of .864 and a yield of unclustered powder of only 57.2%.

Example Nine hundred and seven parts by weight of a double base smokeless powder, containing 20% nitroglycerine, pressed through a 0.045 inch die having a 0.015 inch pin, and the strand so produced cut into 21 particles per inch, was placed in a sweetie barrel maintained at 75 C. To this was added 36.2 parts by weight of ethyl ortho benzoyl benzoate dissolved in 136 parts by weight of isopropyl alcohol and the mixture was tumbled for 1 hour at 75 C. leaving the lid off the barrel during the last 30 minutes. The powder was removed and dried for 8 days at 55 C., then graphited, screened and exposed to an atmosphere of 50-60% relative humidity to bring the moisture content to equilibrium. A yield of 92% of unclustered powder was obtained.

It will be understood that the foregoing examples are by way of illustration only, and that the scope of my invention is not to be limited thereto, except as hereinafter defined by the claims.

What I claim and desire to protect by Letters Patent is:

1. Smokeless powder grains surface coated with a lower alkyl ester of ortho benzoylbenzoic acid having a melting point within the range from about 35 C. to about 110 C.

2. Smokeless powder grains surface coated with about 1% to about 10% by weight of a lower alkyhester of ortho benzoylbenzoic acid, having a melting point within the range from about 35 C. to about 110 C.

3. Smokeless powder grains surface coated with ethyl ortho benzoyl benzoate.

4. Smokeless powder grains surface coated with methyl ortho benzoyl benzoate.

5. Double base smokeless powder grains surface coated with a lower alkyl ester of orthobenzoylbenzoie acid having a melting point within the range from about 35 C. to about 110 C.

6. Double base smokeless powder grains surface coated with ethyl ortho-benzoylbenzoate.

7. Double base smokeless powder grains sur-: face coated with methyl ortho-benzoylbenzoate.

ELTON R. ALLISON. 

